TtEf'REATTVE SCIENCE. 





Pig. 



tho insidn when tho trick in explained. A board, H H, Li fixed 

 at tii.- bottom ; it is slightly inclined, and forma an angle with 

 tli- line in- In thin board is cot a groove, which in Mini* 

 uiruulur and zigzag, in order that the course of tho ballet, which 

 is j.ii t ml" the groove a, may be obaerved for a long. 

 Of ooarae the groove must be very smooth, and to prevent the 

 l.ull.-t .stopping, it may be rubbed with blaok-lead and polished, 

 tho moro so because the board H H is purposely inclinod 

 very slightly to allow the ballet to movo with comparative 

 slowness, which latter ia inserted at a small hole in one aide of 

 the box, and falla out of another hole in tho door. 

 H M is nn inclinod piano mirror, plaood with tho 

 reflecting face towarda tho aloping board 11 n. 

 B is the oyo of tho spectator looking through an 

 aporturo in the box, so arranged that whilst tho 

 grooved board ia invisible, the reflection only 

 in the glass ia aeon. Tho light may bo admitted 

 through the closed door, which may bo a frame 

 door covered with fluted groon silk of a light 

 shade. It may easily be understood from what 

 has already boon explained with respect to tho 

 properties of plane mirrors, that the reflection of 

 tho board H u with the groove and bullet B will 

 appear almost vortical, and as if it was the sido 

 of tho box facing tho eyo at 8 ; and as the bullet 

 rolls down the p 

 groove in tho in- 

 clined plane n H. 

 it will appear to 

 ' tho ser- 

 pentine path PP, 

 as indicated by 

 the dotted lines. 

 It must be re- 

 memborod that 

 tho light illumi- 

 nating the in- 

 clino of tho box 

 comos from tho 

 fluted green silk 

 door, not shown 

 in the drawing. 



To construct 

 a six-sided box, 

 in which a num- 

 ber of different 

 objects are visi- 

 ble, when ob- 

 served through 

 holes in each 

 face of the hexa- 

 gon: 



Let ABCDKP 



(Fig. 6) represent a six-sided box divided into 

 six equal compartments by plane mirrors with 

 their reflecting surfaces directed towards each 

 peep-hole, shown by the black dot in each 

 side. If, then, a separate article is suspen- 

 ded from tho top in each division, it under- 

 goes an amusing multiplication, and is diffe- 

 rent for each aperture to which the eye is 

 applied. The box and its contents are 

 lighted by a ground-glass, lantern-shaped top, 

 indicated by the lines meeting at the ring G, 

 to which a cord may be attached, that it may 

 hang in a conservatory or other ornamental 

 place, and thus enable a number of persons 

 to look into it at the same time ; and if they 

 ask one another what they have seen, some fun may bo caused 

 if the objects are properly selected. 



With cylindrical or conical mirrors very amusing distortions 

 of tho figures are produced, which, if drawn on paper, may in 

 their turn be reversed and made to appear straight again. 



By any of the new silvering processes the interior of a glass 

 cylinder is easily covered with bright metallic silver, or a 

 cylinder may be formed of the best Britannia metal, and being 

 liighly polished, is placed in a circle around which the distorted 

 is delineated. 



Fig. 7. 



A B (fig. 7) represents the cylindrical mirror in which th 

 distorted drawing, u v, ia represented in it* true proportion* 

 The difficulty or perhaps young people would say the amuse- 

 ment ia to draw the distorted figure*, which are designed ia 

 the following manner : 



Let ABO (Fig. 8) be the base of a portion of the surface of 

 a cylinder of polished metal, which is to be used as the mirror 

 to convert the distorted drawing into the ordinary one, and let 

 A c be the chord of the arc A B 0. On the radius and perpendicular 

 to A c, and prolonged indefinitely, lot the point o be taken. This 

 point o should be at a moderate distance from 

 the mirror, and raised three or four times the 

 diameter of the cylinder above the plane of the 

 base. It is right that the point o should be at 

 such a distance from the mirror, that the lines 

 o A, o o, drawn from tho point o, form with the 

 cylindrical surface a moderately acute angle ; 

 becauae if the lines o A and o c were tangents to 

 the points A and c, the parts of tho object seen 

 through these radii would be extremely contracted, 

 and seen loss distinctly. The point 6 being then 

 thus determined, and having drawn the lines O A, 

 o c, draw also A D and c B to any convenient dis- 

 tance, and in such a manner that they form with 

 the cylindrical surface or the circumference of 



its base equal 

 angles to those 

 which form with 

 them the lines 

 o A, A B ; in such 

 a manner that 

 if the lines O A, 

 O c were re- 

 garded as the 

 incident rays of 

 light, then A D 

 and c B would 

 be the reflected 

 rays. Divide A c 

 afterwards into 

 four equal parts, 

 and form a 

 square above, 

 which must be 

 again divided 

 into sixteen 

 little equal 

 squares. After 

 that draw to the 

 points of divi- 

 sion, 2 and 4, 

 the lines o 2, 

 O 4, which cut 



the mirror at p and H, from which points 

 you carry F G, H I in such a manner that the 

 last lines be the reflected rays of light, which 

 will correspond with tho lines o F, o H, the 

 latter being considered as incident rays of 

 light. That done, on the end o (Fig. 9) of 

 line which may be indefinitely prolonged, 

 draw o N (Fig. 9) equal to the height of th 

 eye above the plane of the mirror ; make 

 o Q (Fig. 9) equal to O A (Fig. 8), and raise 

 on the point Q (Fig. 9) the perpendicular Q 4, 

 equal to F G (Fig. 8), which may be divided 

 into four equal parts ; after which, through 

 the point N (Fig. 9), and tho points of divi- 

 sion, you may draw the straight lines which 

 prolonged will cut the line o p Q (Fig. 9) at the places marked i., 

 ii., iii., iv. Transfer the division in the same order, and the 

 rays A D, c E (Fig. 8) in such a manner that A i., A. ii., A iii., 

 A i- v. be respectively equal to Q i., Q. ii., Q iii., Q iv. (Fig. 9). 

 Proceed in the same manner to divide the lines F, G, H, i 

 (Fig. 8) into unequal parts, as F i., F. ii., F. iii., F iv., and H i., 

 H ii., H iii., H iv. ; then divide in the same manner the line 

 B iv. (Fig. 8). It only remains to join by curved lines the equal 

 points of division on the five lines, which is easily done by using 

 a flexible ruler and pressing it on these points. But as it ia 



Pig. 8. 



